Critical social theory has an uneasy relationship with utopia. On the one hand, the idea of an alternative, better social order is necessary in order to make sense of its criticisms of a given social context. On the other hand, utopian thinking has to avoid bad utopianism, defined as lack of connection with the actual historical process, and finalism, defined as closure of the historical process. Contemporary approaches to critical social theory endeavour to avoid these dangers by way of a post metaphysical strategy. However, they run up against the problem that utopian thinking has an unavoidable metaphysical moment. Rather than seeking to eliminate this moment, therefore, they should acknowledge its inevitability. The challenge is to maintain a productive tension between closure and contestability and between attainability and elusiveness. The paper outlines a strategy for meeting this challenge, a strategy that is based on a distinction between the metaphysical content of utopian projections and their fallible claims to validity. Key Words: critical social theory  fallibilism  metaphysical closure  postmetaphysical thinking  reflexivity  regulative idea  utopia.